For those who missed Ninja Scroll this was their first experience with uncensored gore and nudity in anime. even having seen NS it's easier to stomach those things when it's cool adult samurai driving the action rather than teenage girls. Shocked a lot of people in the mid 2000s who either walked away thinking it was compelling or trash shock value with very little in between.
You had one side that felt pity for Lucy, found justice in her acts of violence that are in retaliation to other threats of violence, saw her as more of a victim than villian, wanted to see her live a life of normalcy with Kouta who is apparently the only kind human in Japan. Felt for the PTSD expressed by both Kouta and Lucy as well as all the forms of abuse against people that couldn't defend themselves. Were attracted to her design and didn't mind the fanservice scenes. There are some themes of discrimination/racism against the unknown, nature versus nurture (are the diclonius inherently evil? or are they a reaction to their environment? are humans more monstrous than they are?) that were received well. Bought into the theory that the diclonius are designed by God as a test to the human race. If they're evil, they get wiped out and the world is repopulated. Kind, then nothing changes.
Then you had the other side too grossed out by the entirely unnecessary fetishization, entirely uncessary incestual romance, gore that goes beyond just simple mutilation (can see skin tearing apart, bones visible), out of place fanservice scenes to care about anything else going on. Doesn't feel that bad for a literal weapon of mass destruction that kinda sorta deserves to be discriminated against for being capable of ending the entire planet if she so chose (nearly does in the manga). Doesn't buy the theory that the diclonius are designed by God to punish the cruelty of the human race when it takes only one person to ruin it for the entire planet.
When I first came across Elfen Lied I belonged to the first line of thinking. Gave the manga a 10/10. Totally sympathized with Lucy. Liked her design. A lot. Saw her as a hero in a world where basically everyone is a bytch and kinda sorta deserves what happens to them.
Recently watched it again some ten years later and now I lean more towards it being mediocre, maybe slightly above in the unintentionally funny dubbed version. It does hang itself with fanservice scenes that feel totally out of place in a horror. I feel less bad for Lucy since mass murder isn't an appropriate response to bullying nor a kid lying about the gender of his cousin. I still think the way the diclonius race is juxtaposed against the lowness of humanity is done well. That scientist with the glasses is a good character, Lucy is always interesting when on screen. The anime original ending is probably better than what the manga devolves into, am a fan of ambiguous endings that can be interpreted in a number of ways. also has a memorable theme song
giving it a 5-6